It may take us a while to fully appreciate the depth and breadth of Barack Obama's historic election. The size of his victory can be seen in the electoral map. In addition to the states that Al Gore and John Kerry won, Obama carried Virginia and Indiana, which haven't voted for a Democrat since Lyndon Johnson swamped Barry Goldwater in 1964. He was even close in Georgia, and leading narrowly in North Carolina as of this morning.

For the last generation, Democratic candidates have struggled against a powerful social and electoral tide. Jimmy Carter eked out a 50.1% victory in 1976. Bill Clinton never broke 50% in his two elections. Obama won last night with 52% of the popular vote – the highest for a Democrat since 1964.

The depth of his victory was expressed by a friend who said last night, "they can't take it away from us this time". Delaware Democrats gathered in the same hotel eight years ago when the television networks declared Florida for Al Gore, and then yanked it back. The memory of that night and the chaos that followed still burns for millions of Democrats. The debacle in Florida was followed by the most excruciating presidential tenure in our lifetime – worse than Richard Nixon's long national nightmare, which mercifully ended two years early.

The longing for redemption goes further back than the last two elections. It goes back to that horrific year when Martin Luther King, Jr and Robert Kennedy were assassinated. Kennedy himself captured that longing when he announced to a shocked crowd in a city neighbourhood that King had been shot:

What we need in the United States is not division; what we need in the United States is not hatred; what we need in the United States is not violence and lawlessness, but is love, and wisdom, and compassion toward one another, and a feeling of justice toward those who still suffer within our country, whether they be white or whether they be black.

Two months later, Kennedy himself was shot and killed. Instead of wisdom and compassion, what we got were 40 years of Republican dominance ushered in by Richard Nixon's southern strategy that played on white fear and resentment of the wrenching social changes of the 1960s. These divisive campaign tactics kept Democrats off balance for 10 presidential elections – until now.

Attempts to paint Democrats as unpatriotic, as soft on communism, as soft on terrorism, as soft on crime, as socialists, as godless atheists no longer worked this time. Attacks that had Democrats cowering for a generation have lost their sting. And surprisingly, the demise of the southern strategy and the culture war was brought about by a black man, who caught the mood of America by telling us that we are not captive to the past, and that we have overcome even deeper divisions in our history.

Last night, Obama cited the story of Ann Nixon Cooper, who voted yesterday at the age of 106. He said she witnessed two world wars, a depression, the civil rights revolution, the moon landing and the fall of the Berlin Wall. And yesterday, Obama declared that this woman born of slaves "touched her finger to a screen and cast her vote, because after 106 years in America, through the best of times and the darkest of hours, she knows how America can change".

Martin Luther King once proclaimed that "the arc of the moral universe is long, but it bends toward justice". One election does not in itself bring about justice, and no political party can rightly claim to hold the key to universal moral truth, but Obama's victory represents that our country's divisions will not last forever, and that, after long last, America is surely turning towards a more perfect union.